Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely non-derivable behavior: per-call pricing of $0.002 USDC via x402 across Base, Solana or Arc, and that failed calls are not charged — material cost information for an agent deciding whether to invoke.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tight sentences: contents first, scope limit second, cost last. No filler, though the payment sentence is dense with chain names that could be trimmed if cost were surfaced elsewhere.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return-value explanation is unnecessary, and the description covers payload contents, page-scope limitation, and payment behavior. Only the omission of when to reach for a sibling instead keeps it from being fully complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is a single parameter and schema coverage is 100%, with the schema already documenting the 1-100 range and default of 20. The description adds nothing about the limit parameter, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource and enumerates the returned fields (make, model name with battery size, availability text, EV-Database detail URL). It is clear what the tool does, but it does not distinguish itself from adjacent siblings such as travel_plugshare or travel_data_wa_gov_electric_vehicle, which an agent could plausibly confuse it with.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Only the models on that page are returned; specs such as range are not on the list' gives a concrete when-not-to-use condition, steering agents away from spec lookups. No alternative tool is named for the excluded cases, so it falls short of full routing guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.